Given wrong contract

i got a call from Sales person wanting me to take up a contract with Cell C but instead i asked if he had any wifi contract. He then told me about few contracts that he had. At the end of the call, we agreed that i will get a mobile wifi contract for 399 per month where i will receive 20GB per month. And he explained to me that because i had receive my wifi in the middle of the month, my bill would be pro-rated. So i received 7GB from the 21st of Oct till month-end and on the 1st of Nov, i received 20GB data as per agreement. I received a wifi message saying that i owe R1347 then i called in the customer service number to understand what was going, the lady who answered the phone confirmed to me that the amount was wrong and my contract is 399 per month. I asked her to send me an sms or email confirming that but she never did. Then i receive my statement again with the same amount that she said it was an error, called in again and i was advised that the person who sold the product to me gave me the wrong product. I then asked to cancel the contract and asked them to pick it up. I am seriously disgusted for being **** to. I have been sent around to different departments like a fool.